If five of the NBA's 6th man players on five different teams signed on one euroleague team, could that make them an automatic championship team, and will a "signing-NBA player limit" rule be introduced?

1.It couldn't make them automatic championship team. Contenders I guess, but it also depends who are these 6men. Teams like Barca or Panathinaikos would take down those random 6men teams. Europe is no China.

2. "signing-NBA player limit" rule would not be introduced. Every league has different foreign players rules or limits. But best teams play in several competitions and has absolute freedom in market. Like in Soccer, there is no cap spaces or smth. rich teams dominates.
And Euroleague is just a international competition. It's not even a real league, it just selects best European teams from different leagues and thats it. It can't limit any signings, because afterall, it's not even their teams...

One thing. It's way harder to judge Euro players individual talent. Because it's all about the team. NBA is way more talented, but it happens, that mediocre or just Euroleague bench warmers looks better in the NBA, for example Omer Asik, Aleksandar Vujacic, Omri Casspi or Brandon Jennings. The same gamestyle is different. Ty Lawson may be better NBA player than Juan Carlos Navarro, but in Europe, it's opposite. So it's hard to judge European teams talent just like that. For NBA fans it may look weak, but it's not necessary true.
And finally, as I said, to win in Europe, you have to play like a team. Like we saw in FIBA, which is very similar to European basketball, even best talent in the world can lose and sometimes, even best players can't translate their game well. like Dwight Howard, who ironically was bad defensively.
you also need bench. Best European teams has very strong bench, their bench is basically the same strong as their starting lineup. It helps to get ready against any matchup and always show something new. You usually can't say who will be da killer, 6-8 guys can lead team to victory, it depends whos hot that day.

All these players in Tranes list looks very good for Euroleague, but I would say who IMO would be EL disappointments :
Birdman (almost sure)
Omer Asik (never ever was good EL player, he suited for the NBA)
Gortat (same. one dimensional defenders are not great in EL. EL has no super talented players and it's more a team game, so EL do not need one dimensional defenders as NBA teams)
Barbosa (didnt impressed me FIBA championships, way worse than Marcelo Huertas)

Mhm.. It would be most talented team in Europe, thats for sure, but still they wouldnt win the league in first season they are playing together. But if u are adding a player like Ginobilli who actualy played Euro/International ball to a team like Panathinaikos I would be surprised if they wouldn't win it all.